This invention relates to powder metal components and the process used to make them. In particular, this invention relates to a method of making parts having complex shapes using powder metal compaction.
Powder metallurgy provides a method of forming metallic parts. Making a part from powder metal typically includes the steps of filling a tool and die set with a powder metal powder, uni-axially compacting the metal powder using the tool and die set to form a powder metal compact, and sintering the powder metal compact to bond the particles of the powder metal compact together to form a final powder metal part. Although the final powder metal part is usually less than fully dense, a powder metal part has exceptional dimensional accuracy in comparison to parts made using other metal fabrication techniques.
To form the top side features in a powder metal compact, between the fill and compaction step, powder metal from the lower portion of the die is transferred upward by the relative movement of the lower tool members. If properly done, this powder transfer moves the powder to the appropriate location within the die cavity for compaction while simultaneously maintaining a powder fill to final part ratio of approximately 2:1 over the different vertical columns of the die cavity in the direction of compaction. If the powder fill to final part ratio is not maintained across the various features of the part, then the final part may have unacceptable variations in density.
Even though some parts having complex shapes can be made using powder metallurgy, certain geometries cannot be produced as a single part using the above-described techniques. To make powder metal parts having these geometries, two or more sections of the part need to be separately compacted and then joined together after compaction. However, two or more separate compaction steps and a joining step is time consuming, costly, and is likely to require significant post-sintering secondary operations.
Hence, a need exists for a way to form powder metal parts having complex geometries.